Bike Fit - Saddle Height DIY

photonic69
photonic69 Posts: 2,416
edited April 2018 in Training, fitness and health
After reading the Bike Fit book by Phil Burt (British Cycling and Sky Physio https://www.britishcycling.org.uk/knowl ... hil-Burt-0 )

I decided to get my bike set up as per his advice. I've found it very useful and no longer get stiff backs, sore necks and aches in my knees.

Last weekend I decided to set my children's (11 & 14) saddle height using the Lemond 0.883x Inside Leg Measurement so duly measured them both and applied the formula. It was wildly out. I would have to raise each of their saddles by 5-7cm!! It was obvious that this was way too high. I had set them both originally set up on turbo with heels on pedals and backpedaling and setting saddle to ensure a very nearly straight leg at the bottom of stroke.

Out of interest and to double check my measurements, I redid mine as per 0.883x my inside leg and it was spot on. Back to the kids to see if I had made an error, but no, same way out readings.

Is there a range at which the Lemond method doesn't work? Both have 170mm cranks so not massively long. I'm confused....


Sometimes. Maybe. Possibly.

Comments

  • keef66
    keef66 Posts: 13,123
    I think you've answered your own question there.

    I've always been wary of fitting advice which relies solely on formulae or specific numbers, and prefer the practical approach you first describe.

    I doubt Mr Lemond ever intended his formula to be applied to fitting childrens' bikes, and I imagine it would be similarly useless for adults with unusually long or short legs. I'd guess that the ratio of crank length to leg length is important.
  • veronese68
    veronese68 Posts: 27,297
    I've never used a formula, I stick the middle of my foot on the pedal and lock my leg straight with the pedal at the bottom of it's stroke. Works for me and isn't relying on any formulas or calculations and has minimal faffing about.
    Kids may like a saddle to be lower than is ideal as depending on their confidence getting their feet down easily may be more of a priority. At 11 I think my daughter would have done, my son not so much.
    Kinesis Pro6
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  • sungod
    sungod Posts: 16,522
    there's no scientific basis to the lemond or any other calculation based method, none have enough parameters to encompass all the ways peoples vary

    best way is probably dynamic, but static gets you close if you are careful

    i found steve hogg's articles on height/set-back helpful as i was tweaking position, particularly on getting set-back correct...
    https://www.stevehoggbikefitting.com/bi ... can-it-be/
    https://www.stevehoggbikefitting.com/bi ... oad-bikes/
    my bike - faster than god's and twice as shiny
  • photonic69
    photonic69 Posts: 2,416
    Thanks for the input chaps. Most appreciated. The Steve Hogg blog is a really interesting read. Some very good tips and pointers. Both kids are very proficient cyclists and are part of a local youth cycling club and my son rides out on 50 mile jaunts with my club. I suspect my daughter will be joining us on some shorter rides soon. I just wanted to make sure that they have the best possible bike fit I can reasonably give them with the added factor they grow so fast!

    I've stuck with the "leg straight at 6pm and heel on pedal" measurement for now as well as riding behind looking at hip sway and then side on when on the circuit.

    I just can't get my head around why the x.883 should give such an erroneous reading as you are measuring from BB center to saddle top. OK, the cranks could be 5mm shorter but to give an error of 5-7cm doesn't make sense to me. There must be a leg length below and above a range where this doesn't work. I'd be interested to see if other riders with legs shorter than 27" and longer than 34" can apply this formula to their saddle heights with good effect.


    Sometimes. Maybe. Possibly.

  • keef66
    keef66 Posts: 13,123
    Having dismissed your formula I discover it's pretty much spot on for me. When I bought my first proper road bike they spent quite some time on the fit, and saddle height in particular. I've been using that measurement ever since and been extremely comfortable. So maybe Mr Lemond's formula works for Mr average most of the time.
  • stevie63
    stevie63 Posts: 481
    I'd imagine it's because 170mm cranks for a kid is far too long (though this is a bit of an assumption because your kids could be 6 foot tall, you don't mention height in your OP), they would be better off with something that was about 140-150mm. That would put the saddle height out by a few cm
  • photonic69
    photonic69 Posts: 2,416
    Hi Stevie63 - yes, ideally you'd replace cranks as the children grew but as crank lengths are very limited anyway and changing very expensive it is not an option. I think the current cranks are 170mm. The kids are now the size of small adults so realistically the smallest crank size commercially available is around 165 so not a great deal of difference. Not enough to make up the 5-7 cm discrepancy I'm seeing with Mr Lemond's formula.

    Found this interesting article about crank length whilst researching this:
    http://bikedynamics.co.uk/FitGuidecranks.htm

    So from this 160mm would be ideal but it probably wont be long before 170mm is ideal too.


    Sometimes. Maybe. Possibly.

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